Furnace regulation



April 27 1926. 1,582,648

6. H. GIBSON FURNACE REGULATION Filed May 25, 1918 2 Sheets-Sheet 1 INVENTOR ATTORNEYJ 20 ,7, yfwv 13M? fl April 27 1926. 1,532,648

G. H. GIBSON FURNACE REGULATION F iled May 25, 1918 2 Sheeis-Sheet 2 INV OR #124 ATTORNEYJ Patented Apr. '27, 1926.

UNITE sTArEs GEGRGE H. GIBSON, 0F MONTGLAIR, NEW JERSEY.

FURNACE REGULATION.

Application filed May 25,

To all whom it may concern:

Be it-known that 1, Greece H. GIBSON, a citizen of the United States of America, and a resident of Montolair, in the county of Essex, State of New Jersey, have invented a certain-newand useful Improvement on Furnace Regulation, of which the following is a true and exact description, reference being had to the accompanying drawings, which form a part thereof.

My present invention comprises improved means for controlling combustion in furnaces such as steam generating boiler furnaces, and the primary object of the invention is to provide effective means for automatically proportioning the amounts of primary air supplied to such a furnace and supporting combustion therein, and to combine therewith provisions for maintaining a predetermined pressure in a combustion chamber of the furnace. Other and more specific objects of the invention are to provide improved regulating means for, but not necessarily limitied to use in effecting the first stated object of the invention, and to pro vide novel means for supplying the secondary air above the fuel bed of the furnace.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding, of the invention, however, and its advantages reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described preferred embodiments of my invention.

Of the drawings:

Figure 1. is a somewhat diagrammatic representation, with parts broken away and in section, of a steam generating boiler furnace and combustion control apparatus associated therewith.

Figure 2 is apartial section taken on the line 22 of Figure 1.

Figure 3 is apartial section taken on the line 3-3 of Figure 1. I

Figure 4 is adiagrammatic representation, with parts broken away and in section, of a steam generating boiler furnace provided with a modified form of regulating apparatus.

Figure 5 isa partial section on the line 5 5 of Figure 4.

Figure 6- isa view of the same general 1918. Serial No. 236,450.

la r type, in which A is the ash pit, A the portion of the combustion chamber above the fuel bed separating this chamber from the ash pit beneath it, and A the portion of the combustion chamber lying beyond the bridge wall B. The throat or passageway above the bridge wall connecting the combustion chambers A and A is divided up into a plurality of tortuous passages by vertical posts 0 and C of refractory material, shown in the form of posts or columns ar ranged in two staggered rows. The secondany air for burning the combustible gases rising from the fuel bed, is supplied to the furnace through aconduit or channel B in the bridge wall. This conduit, which may be open at the ends to the atmosphere. discharges air into the throat connecting chambers A and A", through-a plurality of dis- 4 charge ports or tuyeres B As shown, each port B opens at its upper end immediately back of a corresponding post C[ The primary air for combustion is supplied to the ash pit A through the discharge conduit D of a fan or blower D, operated by a steam motor D The latter is supplied with the necessary steam motive fluid through a branch pipe D connected to the steam pipe 1- of the boiler. The supply of steam through the pipe'D to the motor D is controlled by a throttle valve F, having its operating stem connected to the diaphragm ofa fluid pressure device G. This diaphragm has one side exposed to the pressure of the atmosphere and the other side exposed to the steam pressure transmitted from the steam pipe E through the branchpipe G. The

device G, shown in Fig. 1, is identical in construction with the device G shown in section in Fig. 6. The purpose of the device G, and the valve F controlled by it, is to so vary the amount of primary air supplied to the furnace as to maintain a constant steam pressure in the boiler. The stack draft to which the furnace is subjected is controlled by a damper H, located in the stack connection A of the furnace, and adjusted by the reversible electric motor I. The latter is connected to electric supply conductors l and 2 to cause the motor to run in one direction or the other, or is disconnected il 0m said conductors by an automatic switch mechanism collectively indicated by the symbol J. This switch mechanism comprises a pivoted switch arm J carrying con-. tacts bridging stationary contacts J and J when the switch arm J is swung in one direction from a neutral position, and bridging contacts j" and y' when the switch arm J is swung in the opposite direction from the neutral position shown in Fig. 1. lVhen the conduits J 2 and J 3 are bridged by the switch arm J the motor I is caused to run in the direction to decrease the throttling effect of the damper H. In the neutral position of the lever J, shown in Fig. 1, the motor I does not run in either direction, and thereby maintains the stack damper H in whatever adjustment it may then be in.

The switch arm J is carried by a pivoted balance member K supported by a knife edge pivot K. The balance K comprises oppositely extending horizontal arms on which are hung receptacles L, M, N and 0. As shown, the receptacle L is suspended from the outer end of one of the horizontal. arms of the balance K, and the receptacle 0 is suspended from the outer end of the other horizontal arm. The receptacle M is suspended from the same arm as the receptacle L at an adjustable distance between the receptacle L and the pivot K, and the receptacle N is suspended from the other horizontal arm at an adjustable distance between the receptacle 0 and the pivot K. The upper end of the receptacle L is connected by a flexible conduit P to a straight portion of the primary air supply conduit D, and in such manner as to transmit the static pressure in the conduit D to the upper end of the receptacle L. A Pitot tube Q in the conduit D is connected by a flexible conduit P to the upper end of the receptaclc O. The lower ends of the receptacles O and L are connected by a flexible conduit P The receptacles O and L and the conduit P are partially filled with a suit able sealing liquid which may be water or oil, and which is caused to flow from the receptacle 0 into the receptacle L or back, accordingly as the flow of air through the conduit D increases and decreases. The upper end of the receptacle N is connected by the flexible pressure transmitting pipe P to the combustion space of the furnace. As shown, the pipe 1? leads fromgthe throat cpnnecting the combustion chambers A and The lower ends of the receptacles M and N are connected by a flexible conduit 1, and these receptacles are partially filled with a suitable sealing liquid which may be the same as the sealing liquid partially filling the receptacles L and 0. The upper end of the receptacle M is open to the atmosphere at M. A central depending arm from the balance member K supports an adjustable balance weight K Normally this weight K is so adjusted that the balance member K is in neutral equilibrium when the liquid level in the receptacles L and U are the same, and the liquid levels in the receptacles N and M are the same, so that any displacement of liquid from one receptacle to another tends to produce a corre sponding turning movement of the balance member K about its pivotal axis.

\Vith the apparatus described the passage of air into the ash pit, through the conduit D, results in a pressure at the inlet to the Pitot Q, and hence in the air space above the liquid in the receptacle O, which is greater than the static pressure in the couduit D, transmitted to the air space above the liquid in the receptacle L. In consequence the flow of air through the conduit D causes a displacement of liquid from the receptacle O into the receptacle L, which is a function of the rate of llow through the conduit D. According to well-known laws of fluid flow the displacement of liquid thus produced, will be approximately proportional to the square of the volume of flow through the conduit D. Similarly, the displacement of liquid from the receptacle M into the receptacle N will be proportional to the amount by which the pressure of the atmosphere exceeds the pressure in the throat or passageway connecting the combustion chambers A and A. This pressure dii'i'erential creates, and is a measure of the flow of secondary air into the furnace through the ports B Since the ports B form lixed discharge orilices, the amount of air passing through them into the furnace will be approximately proportional to the square root of said differential between the pressure of the atmosphere and the pressure in the throat or passagewa connecting the chambers A and A.

Since the displacement of liquid from the receptacle 0 into the receptacle L tends to turn the balance member K in a clockwise direction. while the displacement of liquid from the receptacle M into the receptacle N tends to turn the balance in the opposite direction it will be apparent that the initial balance of the member K will he maintained only in case the leverage, due to excess weight of liquid in the receptacle L. is balanced by the turning moment in the opposite direction due to the excess liquid in the receptacle i. It follows, in consequence. that unless a given increase or decrease in flow through the conduit D is ac= companied by a predetermined increaseor decrease in the amount of secondary air discharged through the ports B, the balance or j andj, and thus cause the motor I to.

adjust the damper H so as to increase or decrease its throttling effect and thereby maintain the predetermined ratio between the amounts of primary and secondary air supplied to the furnace.

Furthermore, the balance K operates to maintain a minus pressure in the combustion chamber which is very small, since but a. relatively minute differential between the pressure of the atmosphere and the pressure in the combustion chamber is necessary to obtain the maximum desired, flow, of secondary air into the combustion chamber. Strictly speaking, the operation of the apparatus effects and depends upon a variation in the combustion chamber pressure, which increases and decreases as the boiler steam pressure falls and. rises; but this'variation is so slight-that the device operates practically to maintain a constant combustion chamber pressure or balanced draft.- It'will be observed that the balance K adjusts the stack damper H in response to changes in the resultant of two op osing control forces. One of these control orces, namely: the pressure diiierential transmitted. to the balance throughthe pipes P andIPflis a measure of the rate of primary air flow through the conduit D, and increases and decreases as f the boiler steam pressure falls and rises, and

ber of the turnace.

hence is a function of the boiler steam load or boiler furnace heat requirements. The,

second control force, namely: the pressure diiferential transmitted to the balance through the inlet M and pipe P is a function of the pressure in the combustion cham- Since the total flow of heating gasesthrough the boiler furnace is kept proportional to the rate of primary air flow through the conduit D, and said primary air flow is controlled by the device G, the latter forms a means for making the total flow of heating gases through the boiler furnace dependent upon the steam pressure, while the balance K acts directly on the stack damper adjusting motor I to make the pressure in the combustion, chamber of the boiler vary with the rate of flow of heating gases through the furnace. \The refractory posts 0 and C, in conjunction with the arrangement of secondary air sup-' ply ports B insure a very intimate and-effective mixture of the combustible "gases passin out of the combustion chamber A with t e secondary air and thus insure-a highly efficient combustion. The sensitivenessof the balance, and the ratio of pressures maintained byit, may be-varied byadjusting the receptacle M and N toward and away from the pivot K, and by raising and lowering the Weight;:.1-K.

In the form of my invention'illustrated in Fig. 4 the furnace proper, and the means for supplyingprimary air thereto in regulated amounts, are shown as identical with the apparatus disclosed in Fig. 1, except that the secondary air is passed into tne horizontal channel B in the bridge'wall BA, through a conduit B The stackydamper HA in Fig. 4 is cormected-to a' piston R working in a fluid pressure motor cylinder R. The latter has its opposite ends connected by pressure transmitting pipes P and P to the cylinder S of a controlling valve. The valve member S." working in the cylinder S, as shown, is balanced and 1 is connected by an arm '1 to the diaphragm 'I" of a pressure motor T, the chamber in which is connected to the interior of the combustion chamber by a pressure pipe P. As shown, the pressure pipe P'opens to the combustion space of the furnace in the passage connecting the chambers A? and A. A pressure motive fluid, as compressed air,

is supplied to the cylinder S. through the conduit S The arm T passes supply h a slot S in the side Wall of the throng cylinder S, servin not only as a passage for the arm T but also as an exhaustiport. An adjustable loading spring T is ,connected to the arm T so as to impart a slight pull to the left on the diaphragm T.

In consequence the pressure in the chamber of the motor T will normally be slightly below that of the atmosphere. The valve.

member S proper is so formed that when the pressure in the pressure chamber of the motor T falls below the desired pressure and the diaphragm '1", through the arm T thereupon moves the piston S to the right from the position shown in Fig. 4, the pressure fluid supplied by the pipe S? will pass a through the pipe P into the left hand end of the cylinder R, while at the same time the right handend of the cylinder R. will be connected through the pi e P, and the. peripheral channel inthe va ve member S to the exhaust port S This will move the piston R to'the right and thereby throttle the stack draft and increase the pressure in j the combustion chamber. ,Similarl when the pressure in the, combustion cham er rises above the desired value the .diaphragm T will displace the valve member S -to the left, thereby connecting the right hand end of the cylinder R to the cylinder S, and the left hand end of the cylinder R to exhaust. This will cause the damper HA to open and 'thereb'yfrestore the desired pressure in the I combustion chamber.

- In-tliis'iorm of my invention the assage of secondary air into the channel B, t rough the passage; B, is regulated by a -sliding throttle valve U connected to a piston U, working in a cylinder U. The right hand end of the cylinder U is connected by a pressure pipe P to a Pitot Q located in the primary air supply conduit Di, and the static pressure in the conduit D is' transmitted to the left hand end of the cylinder ll by the pipe P. A spring U exerts a slight loading force on the piston U, tending to move it to the right. \Vith the arrangement described an increase or decrease in the rate of flow, through the conduit D, producesa corresponding opening or closing movement of the valve or damper U As shown. the conduit B is so shaped at the level of the damper U that slide movements of the damper will produce greater differences in throttling effect when the volume of flow through the conduit D is small than when large. Preferably. as shown, the cross section of the conduit 13 is such that the free area past the damper U in the conduit 1) will be proportional to the square root of the difference between the pressures transmitted to the two ends of the cylinder U. With the apparatus shown in Fig. 4, the amount of primary air suppliedis dependent upon the steam pressure, and the pressure in the combustion chamber of the furnace will be maintained constant and slightly below that of the atmosphere, while the amount of secondary air supplied will depend upon the free area of flow through the conduit B past' the damper U and this area will be proportional to the volume of flow through the conduit D, so that in this form of my invention, as in the first described, the ratio of primary and secondary air supplied is kept constant, while at the same time, the pressure in the combustion chamber is also maintained constant. Certain novel features of construction and arrangement of the apparatus shown in Fig. 4 not claimed herein, are claimed in my divisional application Serial No. 38,446, filed June 20, 1925. v

The furnace in the construction shown in Fig. 6 is shown as essentially the same as that first described, except that the secondary air is admitted at the front as well as the rear of the fuel bed and in close proximity to the latter. At the rear of the fuel bed secondary air is supplied from a horizontal channel B", which may have its ends open to the atmosphere, and which discharges air into the combustion chamber through ports B, which open to the chamher A, through the inclined face B of the bridge wall. Secondary air is supplied at the front of the fuel bed through ports 13 opening through the inclined front wall of a horizontal air supply conduit B, which may also have its ends open to the atmosphere. This arrangement for introducing secondary air insures an intimate mixture of,

the secondary air with the gaseous products arising from the fuel at points in close proximity t0 the'fuel bed. This method of introducing secondary air is especially advantageous when the fuel burned is bituminous coal giving off volatile gases and vapors, which quickly decompose and which it is advantageous to. burn before decomposition can occur.

The stack draft damper H13 in the stack draft connection A of the furnace AA is controlled by a fluid pressure motor G, having its pressure chamber connected by the pipe G to the steam pipe E, the arrangement being such that the damper HB opens and closes as the steam pressure falls and rises. The primary air passing to the ash pit A of the furnace AA, through the conduit D from the blower D, is controlled by a device jointly responsive to the pressure in the chamber A and to the quantity of flow through the conduit D. For this purpose I employ a balance W, which has an adjustable pivot, and has an adjustable arm V connected to the operating arm of a valve FA in the pipe D supplying steam from the pipe -E to the blower motor D One end of the balance WV has suspended from it a bell X, and the other end of the balance has suspended from it a bell X. Both of the bells X and X have their lower edges dlpping into a body of sealing liquid contained in a receptacle X The upper end of the bell X is exposed to the pressure of the atmosphere, but the upper end of the bell X is protected from the direct pressure of the atmosphere by locating it in an enclosure forming a portion of the receptacle X The ,pressure in thefurnace chamber A is transmitted to the interior of the bell X through the pipe. P". The static pressure in the conduit D .is transmitted to the interior of thebell X through the pipe P. The pressure of the Pitot tube Q extending into the channel D is transmitted to the top of the chamber X in which the bell X works. To avoid stuffing box difficulties the bell X is formed with a central tubular portion depending from the top of the bell at the margin of an aperture in the latter and extending into the liquid bath in the receptacle X Telescoping with the tubular portion X is a tubular part carried by the top wall of the chamber X, which dips into the liquid in the lower portion of the tubular portion X. The link connecting the bell X to the balance 1V passes loosely through the tubular part X lVith the construction described the total volume of draft passing through the combustion chamber of the furnace will depend upon the steam pressure and will be automatically varied by the device G in such manner as to tend to maintain a constant steam pressure. At the same time the ballit) ance W will adjust the valve FA as required to maintain a constant ratio between the amounts of primary and secondary air supplied to the combustion chamber, and so as to maintain the pressure in the combustion chamber of the furnace practically constant, since the variation in this pressure necessary to control the admission at secondary air is so slight, as I have already explained, as to be practically negligible.

In Fig. 7 I have illustrated the use of my invention in connection with a heater AB, suitable for use in house heating, and which may be either a hot air, hot water or vapor heater. In this heater the rate of combustion is controlled by opening and closing a damper HG, to therebyadmit more or less atmospheric air into the chimney stack connection A, and correspondingly decrease or increase the efiective draft to which the furnace is subjected. 1) represents an air inlet to the furnace opening into the ash pit of the furnace A, and D" represents a secondary air supply conduit opening to the furnace chamber A above the fuel bed.

the atmosphere. The ratio of primary and secondary air is controlled in this case by a damper HD in the secondary air supply conduit D. This damper is connected by a chain 2* to the gear wheel Z which may be driven in one direction or another through a worm shaft Z by a suitable motor which may be a spring motor. When the gear wheel Z turns in the clockwise direction, the pull of the chain Z moves the valve HD in one direction, and when the wheel Z is rotated in the counter-clockwise direction the valve HD is correspondingly adjusted bv means of the weight Z connected to the lower end of the chain Z and holding the latter taut, As shown, the

motor is provided with two driving gearsf Z and Z which are connected by the bevel gear Z and turn in opposite directions. A.

gear wheel Y splined on theworm shaft.

Z can be moved into mesh with either of the gears Z or Z from the neutral position shown in the drawing in which it is'out of mesh with each of these gears. The motor .Z may be started and stoppediby moving a stop arm Y out of and mto engagement with the escaping device Z of the motor.

The gear'wheel Y is shifted on the worm shaft Z and the arm Y moved into and out of engagement with the escapement device Z by a rod Y connected to the arm Y of a balance lever Y fulcrumed at Y". The arm Y is connected to the rod Y, and with the latter is formed with a hook at its end remote from the balance Y which enters a groove in the hub of the gear Y. The balance lever member Y has two oppositely extending horizontal arms, from each of which isadjustably suspended a bell Y. The

two bells Y dip into a bath of sealing liquid contained in a receptacle Y open at its upper end. The static pressure in a restricted portion of the primary air supply conduit D at which the static pressurev ply conduits D and D into the form of a Venturi sect-ion, and mount in each of these Venturi sections a small Vnturi tube D having its discharge end located at the throat of the large venturi in which it is mounted, I connect the pipes P and P to thethroats of the corresponding small venturis.

With the construction shown in Fig. 7, the balance lever Y will turn in a clockwise direction, or in the contrary direction, accordingly as the ratio of primary to secondary air supplied to the furnace decreases or in-' creases from a predetermined ratio. When the balance lever-Y turns in the clockwise direction the gear wheel Y is movedinto mesh with the motor gear Z and the gear wheel Z is then rotated in the direction to close the damper HD and thereby increase the ratio of primary air to secondary air supplied the furnace. When the balance lever Y swings in the opposite direction from the neutral position shown in Fig. 7 the gear Y is moved into mesh with the gear wheels Z and atthe same time the stop arm Y is moved out of engagement with the esopen the damper HD, and thereby decrease the ratio of primary to secondary air. The ratio of primary to secondary air may be adj usted by adjusting the bells Y toward and away from the pivot axis Y of the balance Y The adjustable weight Y forms a means for calibrating the apparatus so that the balance will be in a condition of neutral equilibrium when the pressure difi'erential ett'ect thereon is zero.

While in accordance with the provisions" of the statutes 1 have illustrated the best form of my invention now known to me, those skilled the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forthin the appended claims, and that some features of my invention may sometimes be used to advantage without a corresponding use of other features of the invention.

Having now described my invention, what LOO I claim as new and desire to secure by Letters Patent, is:

1. The combination with afurnace having a combustion chamber and primary and secondary air supplies, of means responsive to the amounts of primary air and secondary air supplied and to the pressure in the com bustion chamber of the furnace and means controlled by the first mentioned means for maintaining a predetermined ratio between the amounts of primary and secondary air supplied and regulating the pressure in the combustion chamber of the furnace.

2. The combination with a furnace having a combustion chamber and primary and secondary air supplies, of means responsive to the amounts of primary air and secondary air supplied and to the pressure in the combustion chamber of the furnace and means controlled by the first mentioned means for maintaining a predetermined ratio between the amounts of prin'iary and secondary air supplied and for maintaining; a practically constant pressure in the combustion chamber of the furnace.

3. The combination with a furnace having a grate forsolid fuel and a combustion chamber at one side of the grate, a secondary air inlet to said combustion chamber and a primary air inlet to the furnace at the opposite side of the grate, of controlling means responsive to the pressure in the combustion chamber and to the amount of primary air supplied and means controlled by the first mentioned means for regulating the pressure in the combustion chamber and maintaining a predetermined ratio between the amounts of primary and secondary air supplied.

4. The combination with a furnace having a grate for solid fuel and a combustion chamber at one side of the grate, an inlet for atmospheric air opening to said combustion chamber a forced air supply to the furnace at the opposite side of the grate from said combustion chamber, and means responsive to the pressure in the combustion chamber and to the amount of primary air passing to the furnace and means controlled hy the first mentioned means for regulating the pressure in the combustion chamber and maintaining a predetei 1 ratio between the amounts of primary secondary air supplied.

The combination with a furnace having primary and secondary air supplies. of a device for adjusting one of said supplies, and controlling means therefor, comg'irising a compound differential pressure gauge and means for subje s; said gauge to a differ-- ential pressure which is function of the amount. of primary air supplied and to an opposing dilierez pressure which is a function of the amount of secondary air supplied.

' and incieascs, means ror 6. The combination with a furnace having primary and secondary air supplies, of a device for adjusting one of said supplies, and controlling means therefor comprising a tilting differential pressure gauge of the sealing liquid displacement type. and means for eifccting a displacement of the gauge scaling liquiu which a measure of the amount of primary air supplied, and simultaneously effecting and opposing liquid displacement which is a measure of the secondary air supplied.

7. The combination with a furnace having separate primary and secondary air inlets, of means responsive to the dillerr-utial between the pressure of the atmosphere and the pressure in the furnace, means responsive to the amount of air entering the furnace through the primary air inlet and means jointly controlled by the two means first mentioned for maintaining a prudetermined ratio between the primary and secondary air entering the furnace and For regulating said pressure differential.

8. The combination with a furnace bavin; a combustion chamber and a secondary inlet to said chamber from the atmosphere of fixed resistance. and having a separate primary air inlet, of means jointly responsive to the amount of air passing into the furnace through the last mentioned inlet and to the difference between the pressure of the atmosphere and the pressure in the combustion chamber and means controlled by the first mentioncdnieans for maintaining a predetermined ratio between said differencein pressure and the air passing through said mentioned inlet.

9. In a'boiler furnace cornlmstion regulating system, the combination or" means for maintaining a control force which increases and decreases with the boiler load requirements, m ans for creating a second control force varying the pressure in the boiler furnace combustion chamber, and a stack damper actuator jointly controlled by said forces.

10. In a boiler furnace combustion rcgulating system, the combination of a device responsive to the boiler steam pressure for maintaining control force whicn increases and decreases as said pressure diminishes creating a second control force varying with the pressure in the boiler furnace combustion chai'nber. and a stack damper actuator subject to the dilferential action of fitlfl forces.

11. in a boiler furnace ron'ibustiou regualting sstem, the conibiration with a (b)- iee responsive the boiler steam prc for controlling t rate of ilou' oi' the l the fur of a (1 ma furnace cons the last mentioned devices to two control forces, on of which is dependent on the rate of flow of the heating gases through the furnace, and the other of which is proportional to the difference between said pressure and t the pressure ofthe atmosphere.

12. In a boiler furnace combustion regulating system, the combination with means regulating the supply of air for combustion to the furnace, and means regulating the escape of products .of combustion from the furnace, of adevice responsive to the boiler steam pressure directlycontrolling one of said means, and a controlling device for the other of said means comprisin a balance and means for subjecting said baIance to two opposing forces, one of which is a function of the boiler steam pressure and the other of which is a function of the pressure in the combustion. chamber of the furnace.

13.,In a boiler furnace combustion regulating-systenn-the combination with means regulating the supply of air for combustion to the furnace, and means regulating the escape of products of combustion from the furnace, of a device responsive to the, boiler steam pressure directly controlling one of said means and control mechanism for the other of said means jointly responsive to the boiler steam'pressure and to the pressure in the combustion chamberof the furnace.

14. In a combustion regulating system for a boiler furnace,the combinationwith means for varying the rate of supply of air for combustion in inverse response to the pressure of the steam generated, of means for regulating the furnace pressure in direct response to thetdifi'erential. between the furnacepressure in the furnace and the pressure of the atmosphere and in inverse response to the steam pressure.

.15. In a combustion regulating system for a boiler furnace, the combination with means for varying, the rate of supply of air for combustion in response to boiler load, of means for regulating the furnace pressure in response both to' the differentialbetween the pressure in the furnace and the pressure of the atmosphere, and to the boiler load.

supply of air in inverse response to the pressure of the steam generated, the combination with 'll'lQCllfll'llSIlIfOl regulating the, furnace pressure, of controlling means for said mech;

anism including a balance, means for sub-' jecting said balance to a force proportional to the difference between the furnace pressure and the pressure of the atmosphere, and

opposing the first mentioned force and increasing and decreasing, respectivel ,as the pressure of the steam generated decreases and increases. 4

'GEORGE H. GIBSON.

means for subjecting said balance to a force 

